Porque ridículo, sería lo más congruente, el porque el tío Wuzu no envejece, sabiendo que la mamá de Fan Xian viene de un mundo moderno donde la humanidad se extingui por el congelamiento y a Fan Xian le transmitieron los recuerdos de este mundo incluso antes que naciera
We always knew Wuzhu wasn't human and that he could be some kind of robot/cyborg. In Season 1, after seeing all the incredulous things Wuzhu could do, Fan Xian would always say to him "Are you even human?" That's why Wuzhu is practically invincible but it doesn't mean he's immortal or can't be killed. His main directive was to protect Fan Xian and he carried that duty to the utmost. He's one of my favorite characters in this drama!